Electrocatalysis\nof Oxygen Evolution Reaction Promoted\nby CoNiMn Films Synthesized by Electrodeposition

Recently, efforts\nhave been made to address the environmental damage\ncaused by fossil-fuel-based primary energy sources. Interest in efficient\ntechnologies for converting and storing energy using renewable sources,\nespecially sunlight, has increased, with the aim of replicating the\nnatural photosynthesis process. However, artificial photosynthesis\nfaces challenges with unfavorable kinetics and thermodynamics, requiring\nthe use of stable catalysts for the hydrogen evolution (HER) and oxygen\nevolution (OER) reactions to generate H<sub>2</sub> and O<sub>2</sub>, respectively. OER is the most prohibitive of the half-reactions\nby the highly sluggish kinetics. Mixed oxides, particularly those\nbased on first-row transition metals, have shown promising results\nas catalysts for the OER. This work reports the synthesis of CoNiMn\noxide via electrodeposition on fluoride tin oxide followed by electrochemical\nactivation. This approach seeks to explore the synergistic effect\nbetween the elements and to produce a catalyst with superior efficiency\nand stability for the electrocatalysis of the OER compared to the\nmonometallic and bimetallic oxides. The CoNiMn film was structurally\nand\nelectrochemically characterized. The electrodeposited CoNiMn hybrid\nfilms demonstrated low overpotentials compared with standard OER electrocatalysts,\nwith CoNiMn films outperforming all single and bimetallic oxide films.\nThe activated CoNiMn film required an overpotential of 100 mV at 10\nmA cm<sup>–2</sup> (430 mV at 25 mA cm<sup>–2</sup>)\nand Tafel slope of 58 mV dec<sup>–1</sup>. The film was active\nfor 15 h at 100 mA cm<sup>–2</sup> and showed no significant\nchange in morphology and structure after the chronopotentiometry,\nindicating that it is a promising and cost-effective alternative to\nenhance the OER activity using abundant elements.